// trim 
String.prototype.trim=function(){
　　    return this.replace(/(^\s*)|(\s*$)/g, "");
}
//reverse
String.prototype.reverse=function reverse() {
    var str = "";
    var end = this.length - 1;
    for(;end >= 0; end --) {
        str = str + this.charAt(end);
    }
    return str;
}